Conversion of hydrocarbon oils



Patented Mar. 28, 1939 PATENT OFFICE.

2,152,147 CONVERSION OF HYDROGARBON OILS Charles W. Nofsinger,

Summit, N. J., assignor to Gasoline Products Company, Inc., Newark, N. J., a corporation of Delaware Application September 22, 1937, Serial No. 165,025

2 Claims.

This invention relates to improvements in methods of converting higher boiling hydrocarbons into lower boiling hydrocarbons.

According to my invention a relatively heavy 5 oil issubjected to mild cracking conditions to effect viscosity breaking thereof and the production of gas oil constituents to be used as stock to be cracked inother cracking operations in my process. The viscosity broken products are separated into vapors and cracked residue and the vapors are fractionated and separated into a heavy reflux condensate, a lighter reflux condensate and a light distillate product containing gasoline constituents.

The heavy reflux condensate is passed through a cracking zone where it is maintained under superatmospheric pressures and at high temperatures to effect the desired extent of cracking thereof. The cracked products are then passed to an evaporator or separating zone wherein vapors are separated from liquid residue. The vapors are fractionated to separate heavy reflux condensate containing insufficiently cracked products, which is recycled through the cracking zone, from a lighter reflux condensate and from a light distillate having the desired boiling range.

The lighter reflux condensate separated from the visosity broken products is passed through a second cracking zone where it is maintained under superatmospheric pressures and at high temperatures to effect the desired extent of cracking thereof. The cracked products from the second cracking zone are separated into vapors and liquid residue and the vaporsare fractionated to separate a light reflux condensate containing insufficiently cracked products, which is recycled through the second cracking zone for further cracking, from condensate oil such as furnace oil and from a light distillate product having the desired boiling range. The light reflux condensate separated during fractionation of the vapors derived from the first cracking zone is used as reflux in the fractionation of vapors separated from the cracked products coming from the second cracking zone.

To obtain the several fractions for use in the cracking zones in addition to those separated from the viscosity broken products, I may pass a heavy oil such as crude oil to a stripper or frac tionating tower and withdraw the residue at the bottom of the tower for treatment in the viscosity breaking zone. Heavy gas oil, light gas oil, a heavy naphtha fraction and light overhead vapors are separated and maybe withdrawn at different points from the tower and used as. stocks to be cracked in the cracking zones. The naphtha and light gas oil fractions may be combined and passed to the second cracking zone or the naphtha fraction may be separately treated in a reforming zone to enhance the anti-knock value thereof. Overhead vapors from the stripper or fractionating tower are condensed and may be separately collected, or mixed with the naphtha fraction withdrawn from the top portion of the stripper or fractionating tower.

The light distillate containing gasoline constituents separated from the vapors derived from the viscosity broken products may be collected as such, or it may be combined with the naphtha fraction withdrawn from the stripper or fractionating tower for further treatment in a reforming zone, or it may be combined with the light gas oil fraction from. the stripper and. fractionating tower for further treatment in the second cracking zone.

Further features and advantages of my invention will be apparent from the following detailed description taken in connection with the drawing which represents a diagrammatic showing of apparatus suitable for practicing the invention.

In the drawing, the reference character I0 designates a pump for passing a heavy oil charge, such as crude petroleum oil or topped crude, through a line 12. The heavy oil, preferably preheated in any suitable manner to a distilling temperature, is introduced into the bottom section l3 of a stripper or fractionating tower 14 wherein it is subjected to distillation. The tower I4 is provided with trap-out tray l6 having a hood l8, trap-out tray 22 having a hood 24 and trap-out tray 26 having a hood 28. The trap-out trays are vertically spaced within the stripper or fractionating tower l4 so that several fractions may be collected and withdrawn from the tower 14 during distillation and fractionation of the introduced oil.

The vapors remaining after fractionation leave the top of the tower l4 and are passed through line 32, through condenser 34, and the distillate containing gasoline constituents is collected in receiver 36 having a valved gas outlet 38 and a valved liquid outlet 42. A portion of the distillate may be returned to the top portion of the stripper or fractionating tower 14 through line 44 by pump 46 as reflux. If desired, a coil 52 may be used at the top of the tower i l to provide additional cooling for the top thereof. 7

The crude residue collecting at the bottom. of the stripper or fractionating tower I4 is withdrawn therefrom and passed through line 54 by pump 58 and passed through the viscosity breaking zone or coil 68 extending through furnace 84. The products leaving the viscosity breaking zone or coil 88 are passed through line 88 preferably having a pressure reducing valve I2 into the evaporator or separating zone I8 wherein the products are separated into vapors and liquid residue. If desired, a quench oil may be introduced into the stream of products through line 18. The liquid residue is a fuel oil which is withdrawn through line 82 and further treated as desired. The separated vapors leave the evaporator or separating zone I6 through line 84 and are introduced into the bottom portion of the fractionating tower 88' provided intermediate its ends with a trap-out tray 88 having a hood 92. V

'Ihe vapors are fractionated in the tower 86 to separate a heavy reflux condensate as, for example, a heavy gas oil which is withdrawn from the bottom of the fractionating tower and passed through line 94 by pump 96 through the cracking zone or coil 98 as will be later described in more detail. During fractionation a light reflux condensate as, for example, a light gas oil is collected on trap-out tray 88 from which it is Withdrawn and passed through line I 82 by' pump I84 into a second cracking zone or coil I88 as will be later described in more detail.

The vapors remaining after fractionation in the fractionating tower 86 are passed through line I88 and condenser H8, the distillate containing gasoline constituents being collected in a receiver or drum II4 having a valved gas outlet I18 and a valved liquid outlet H8. A portion of the distillate may be returned to the top of the fractionating tower 86 through line I22 by pump I24 as reflux. If desired, a coil may be used at the top of tower 88 to provide cooling therefor.

The heavy reflux condensate which'is withdrawn from the bottom of the fractionating tower 88 through line 84 may be admixed with the heavy reflux condensate which collects on the trap-out tray I8 in the stripper or fractionating tower I4 during fractionation of the heavy oil therein. The heavy reflux condensate from trapout tray I8 is passed through line I28 by pump I32. The mixture of heavy reflux condensates is passed through the cracking zone or coil 98 in the furnace I 38. The stream of products leaving the cracking zone or coil 88 passes through line I42 having a pressure reducing valve I 44 and is introduced into the evaporator or separating zone I 48 under a lower pressure. Before being introduced into the evaporator or separating zone I45 the stream of products may be quenched with an oil passing through line In the evaporator or separating zone I48 the products are separated into vapors and'a liquid residue, the liquid residue being a fuel oil which is Withdrawn through line I48. The separated vapors are passed through line I52 and intro duced into the bottom portion of a primary fractionating zone I58 wherein heavy reflux condensate containing insufficiently cracked products is separated and collected on the bottom thereof. The heavy reflux condensate containing insufliciently cracked products is withdrawn from the bottom of the primary fractionating zone I54 and passed through line I56 and is recycled through the cracking zone or coil 98 by pump I58 to effect'further cracking thereof. f

Before passing through the cracking zone or coil 88 the heavy reflux condensate is preferably mixed withthe heavy reflux condensates to be cracked which are passed through lines 84 and I28 to the cracking zone or coil 98. The heavy reflux condensate passing through line 94 is withdrawn from the bottom of fractionating tower 86 where vapors from the viscosity breaking treatment are fractionated, and the heavy reflux condensate passing through line I 28 is withdrawn from trap-out tray 16 in the stripper or fractionating tower I4 where the heavy feed oil is fractionated. The top of the primary fractionating zone I54 may be provided with a cooling coil I62 to provide. cooling for the top of the primary fractionating zone' I54.

The vapors remaining after fractionation in the primary fractionating zone I54 are passed through line I84 and introduced into the bottom portion of a secondary fractionating zone I68 wherein a separation into light vapors and a relatively light reflux condensate occurs. The relatively light reflux condensate is withdrawn from the bottom of the secondary fractionating zone I88 through line I68 and is directed to another fractionating zone later to be described. The light vapors remaining after fractionation in the secondary fractionating zone I66 pass through line I12 and condenser I74 and are collected as a distillate having the desired boiling range. The distillate is received or collected ina receiver or drum 116 having a valved gas outlet I28 and valved liquid outlet I82. Some of the distillate may be returned to the top of the secondary fractionating' zone I68 through line I84 by pump I88 as reflux.

The light reflux condensate separated from vapors derived from the viscosity breaking treatment is withdrawn from trap-out tray 88 in the fractionating tower 88 through line I82 and is admixed with light reflux condensate such as a light gas oil which collects on trap-out tray 22 in the stripper or fractionating tower I4 and which is withdrawn therefrom and passed through line I 92 by pump I94. The combined stream of light reflux condensates is passed through the .cracking zone or coil I86 extending through the radiant section I98 of the furnace 282. The stream of cracked products leaves the furnace 282 through line 284 having a pressure reducing valve 288 and is introduced into the evaporator or separating zone 288 under lower pressure. Before being introduced into the evaporator or separating zone 288, the stream of cracked products may be quenched with an oil 7 passing through line 2I2.

In the evapo'rator or separating zone 288 the cracked products are separated into vapors and a liquid residue, the liquid residue being with contains insufficiently cracked products and is recycled through the cracking zoneor coil I88 after having been mixed with the light reflux condensates passing through lines I82 and I92 to be cracked in the cracking zone or coil I86.

The relatively light reflux condensate above referred to which is separated from vapors derived from the heavy gas oil cracking operation in zone or coil 98 is withdrawn from the bottom essence of the: secondary fractionating; zone Hi6" and passed? through line I268 by pump 2263 and is in.- troduced into. the, top portion of the. primaryfractionati'ng: zone. 21 8: which; functions: to frac=- tionate vapors. derived from. the: light.- gas. oil cracking operation in zone. or coil Hit; The light. reflux condensate introduced; intofraction. ating tower 218 through line I68 dephlegmates the vapors inthetower 218% to separate heavier: constituents therefrom. and some of the lighter constituents oi the-introduced reflux condensate are. vaporized. The. unvaporized. constituents; of. the introduced reflux: condensate together with: the insumcient-ly' cracked products front the: bottom of primary fractionating; zone: 2;l 8;- abovereferred to. are. directed to the cracking zone: or coil; HIE for further cracking. The vapors remaining; after fractionation: in the primary fractionating zone 2l8' together with vapors: derived from the; introduced light; reflux: condensate: are passed: through line 22 8% and introduced into therbottome portion of the; secondary fractionating zone 23-2. wherein further fractionation takes place andlight vapors are separated from a condensate oil. The condensate. oil is. a. furnace. oil which. collects on the bottom. of the. secondary tractionating. zone 232 and is withdrawn. through. line. 234.. If desired, a portion of the. reflux condensate. from the bottom of. towerv 232. may berefinxed on tower. 2 i 8 at an intermediatepoint therein. and recycled for further cracking, preferably being. introduced. below the point, of. introduction. of. the light re flux condensate. introduced through line. 168..

The separated vapors. from. the secondary fractionating zone 23.2 are. passed. through. line 23.5.;

and condenser. 23.8 and collected as a distillate. having thev desired boiling. range. The distillate.- is collectedin a receiver 242. having. a valved gas outlet244 and a. valved) liquid. outlet. 246. Some of the distillatemay be returned. to. the. top por-- tion of the secondary fractionati'ng. zonev 23.2 through. line 2.48 by pump. 25.2 as. reflux. If desired,. a coil may be used at. the top of'the. sec.- ondary fractionating zone 23.2 to. provide. cooling. therefor.

In order toremove; substantially all of. the light constituents from. the. bottoms, oi the secondary fractionatingzone 23. 2,. the.- bottoms may be passed through line. 254. by pump 2.56 and through the reboiler coil 25.& extending through the convection section 2.60. of. the furnace 2.82.. The heated bottoms are then passed.through line, .262 and returned to. the. bottom portion. of. the secondary fractionating. zone 232.. By using the step of reboiling the bottoms from the. secondary fractionating zone 232,.undesirablelight constitu cuts are removed from the furnace oil. which is withdrawn from the bottom of. the secondary fractionating zone. 232. through line 234. The furnace oil treated. in this way has a. boiling. range to. meet. flash. requirements. In. some. in.- stances it may be desirable. to also. reboil the bottoms from. the. secondary fractionating. zone.

Duringqfractionation of. the. heavy oil in the stripper or fractionating tower M a heavy naph tha fraction containing gasoline. is collected on trap-out tray 26 therein. This naphtha fraction is passed through line 2.64 by pom-pr 2-66: and: all: or part thereof may be: passed through line: 2.68 and mixed with the light refluxicondensatewithdrawn from the trap-out tray and the combined stream passed through line- I92- to the. cracking coil or zone H16. Inthis-waw the naphtha fraction is: subjected to cracking and. re:-

torming'while: the light reflux." condensate: be:-

cracked. Instead. ct passing through line 26 8, the. naphtha. traction may be passed through line. 2.1505 mixed with. the distillate Withdrawn from the. receiver I I747. The mixtureof the: naphthan fraction and the. distillate from. receiver M 4?- derived from vapors separated: from prode ucts obtained. from: the. viscosity breaking treatment bepassed: through acracking; and re:- forming' coil or: zone in order tocrefornrthe. gasoline constituents. and. increase the: anti-knock value. of the motor fuel.

Thel-i'ght'. distillate collected in. receiver 36; durthev fractionation or the heavy oil. in the. stripper or fractionating tower: M may be re.- turned through line 21-25 to the line. 264 and. admixed with the: naphtha fraction withdrawn trons the. trap-out: tray 2% in. the. stripper orfracti'onating tower M2 for further treatment: there.- With: as. above. described.

While I prefer to. use a stripper and fractionating-towet; in some instances: the stripper and fractionating tower M. may be omitted in which event; a. heavy oil such: as reduced crude oil is treated in viscosity breaking: zone or coil 6.0 and: a heavy oil from an extraneous: source is. passed through cracking zone or: coil 98', and: a: light gaso-ilt from extraneous source: is. passed through. the second cracking zone; or coil. ms. The heavy gas oil. ismixed with the heavy reflux condensate derived from: the viscosity breaking treatment and the recycle condensate oil= from the bottom or primary fractionating zone. 1 54*; and the light gas. Ol'li is. mixed with. the light reflux condensate derived? from the viscosity breaking-r treatment and: with the recyclecondensate. oil from the bottom of. primary fracti'onati'ng Zone 24 8? for treatment in the. crackin zones as: above described.

A typical operation according to my invention. will now be given but it isto be understood that 1'5 am not restricted thereto; The charge of heavy cn-rwhich may-be a crude petroleum, topped crude oil: or other heavy oil is: preferably preheated to a distilling temperature about 600 to 7.50" F; before it is introduced into the bottom portion. of the stripper or fractionating tower M where it is subjected: to: distillation to remove all constituents boiling below 650 to 750 F. The M1 maybe maintained under a pressure of atmospheric to about 1-00 pounds per square-inch. The: crude residue collecting at the bottom of the stripper or fractional-ting tower l4 hasv an initialboilihg point of about 650- to 750" F. and is subiected to a viscosity breaking treatment by being passed. through: the viscosity breaking coil or zone 60. which ismaintained under crackingconditions orderto= efi'ectthe desired reduction in. viscosity and the formation of gas oil constituents which can be further cracked under drastic cracking conditionsto produce lower boiling constituents havinghigh anti knock. value. 7

During its" passage through the viscosity breaking coil or zone 60 the crude residue is maintained under a pressure; of; about 100120 300v pounds: per square inch ,and atz'a temperature of about 7-50 to- 9253.5. The: viscosity broken products: leave the viscosity breaking: zone or coil 60 under pressure of about 250; pounds per square inch and at a. temperature of about 900 F.

The viscosity broken: products are introduced intothe evaporator: or" separating zone 16' which is: maintained at a pressure of aboutv 10 to 200 pounds; persquare; inch, prefer-ablyabout 1'5' to separate a heavy reflux condensate such as heavy gas oil from a lighter reflux condensate such as a light gas. oil. The tower 86 is main tained under a pressure of about 10 to 200 pounds per square inch, preferably about v15 pounds per square inch. The heavy reflux condensate having an initial boiling point-of about 650 to 750 F. is at a temperature of about 700 F. and is admixed with a heavy reflux condensate from the trap-out tray I6 in the stripper or fractionating tower I4 and with heavy reflux condensate withdrawn from the bottom of the primary fractionating zone I54.

The mixture of heavy reflux condensates having about the same initial boiling points is passed through the cracking zone or coil 98 wherein the oil is maintained under superatmospheric pressure and high temperature conditions in order to bring about the desired extent of cracking. During passage of the heavy reflux condensates through the cracking zone or coil 98 they are maintained at a temperature of about 825 to 1100 F. and under pressure of about 300 to 1000 pounds per square inch.

The cracked products leave the cracking zone or coil 98 at a temperature, for example, of about 925 F. and under a pressure of about 750 pounds per square inch and are passed to the evaporator or separating zone I46 which is maintained under a lower pressure of about 50 to 200 pounds per square inch, preferably about 110 pounds per square inch. The vapors leaving the evaporator or separating zone I46 are frace tionated by being passed through the primary fractionating zone I54 and secondary fractionating zone I66 preferably maintained at the same secondary fractionating zone I66 is directed to the primary fractionating zone '2I8 wherein vapors derived from products leaving the light condensate cracking zone or coil I06 'are fractionated.

The light reflux condensate separated from the vapors derived from the viscosity breaking treatment is withdrawn from the fractionating tower 86 through line I02 and is admixed with light reflux condensate separated during the fractionation of the heavy oil in the stripp r or fractionating tower l4. The light reflux condensates have an end point of about 650 to 750 F. The mixture of light reflux condensates together with the condensate oil withdrawn from the bottom of the primary fractionating zone 2I8 is passed through the second cracking zone or coil H36 wherein the oil is maintained at a temperature of about 825 to 1100 F. and under; pressure of about 300 to 1000 pounds per square inch.

The cracked products leave the second cracking zone or coil I06 at a temperature, for example, of about 950 F. and under pressure of about 750 pounds per square inch. The cracked products are introduced into the evaporator or separating zone 208' maintained under about 50 to 200 pounds per square inch preferably about 110 pounds per square inch to separate vapors from a liquid residue and the vapors are fractionated by being passed through primary fractionating zone 2I8 and secondary fractionating zone 232.

'densed and the distillate is collected in the receiver 242. This distillate is a light motor fuel such as gasoline and may be further treated as desired.

.The two gasoline products collected in receivers I16 and 242 may be separately treated or may be blended to produce any desired products.

In the preferred form of the invention the reboiler coil 258 maintains the bottoms of secondary fractionating zone 232 at a temperature of about 650 F, which is about 25 degrees higher than the bottoms of primary fractionating zone 2I8.

While I have described a particular embodiment of my invention, it is to be expressly under-4 stood that my invention is, not restricted thereto, and various modifications and adaptations thereof may be made without departing from the spirit of my invention.

I claim: v

1. A process for converting higher boiling hydrocarbon oils into lower boiling hydrocarbons which comprises passing a charging stock comprising residual constituents of crude petroleum once through a single-pass cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to effect viscositybreaking thereof, passing resultant viscositybroken products to a separating zone wherein vapors separate from liquid residue, passing resultant separated vapors to a fractionating zone wherein the vapors are fractionated to form a heavy gas oil condensate and alight gas oil condensate, directing the heavy gas oil condensate to a'recycling cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling hydrocarbons, passing resultant cracked products from said recycling cracking zone to a second separating zone wherein vapors separate from residue, directing resultant separated vapors to a second fractionating zone Wherein the vapors are fractionated to form a heavy reflux condensate and a lighter condensate, cycling said heavy reflux condensate to said recycling cracking zone, directing aforesaid light gas oil condensate to a second recycling cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling" hydrocarbons, passing resultant cracked products from the second recycling cracking zone to a third separating zone wherein vapors separate from residue. passing resultant separated vapors to a third fractionating. zone wherein the vapors are fractionated to form a heavy reflux condensate, an intermediate condensate and a light distillate, cycling the heavy reflux condensate from the third fractionating zone to the second recycling cracking zone, introducing said lighter condensate from the second fractionating zone to the third fractionating zone wherein it is subjected to vaporization and resultant vapors are subjected to fractional condensation to thereby combine constituents of said lighter condensate with the intermediate condensate in the third fractionating zone and withdrawing said intermediate condensatev as a product of the process. 2. A process for converting higher boiling hy drocarbon oil into lower boiling hydrocarbons which comprises subjecting crude petroleum to fractional distillation to produce a crude residue,

a heavy gas oil condensate and a light gas oil condensate, passing the crude residue once through a single-pass cracking zone wherein the residue is subjected to cracking conditions of temperature and pressure to efiect viscositybreaking thereof, passing resultant viscositybroken products to a separating zone wherein vapors separate from liquid residue, passing resultant separated vapors to a fractionating zone wherein the vapors are fractionated to form a heavy gas oil condensate and a light gas oil condensate, combining said heavy gas oil condensates and directing the combined constituents to a recycling cracking zone wherein they are subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling hydrocarbons, passing resultant cracked products from said recycling cracking zone to a second separating zone wherein vapors separate from residue, directing resultant separated vapors to a second fractionating zone wherein the vapors are fractionated to form a heavy reflux condensate, a lighter reflux condensate and: a final light distillate, cycling said heavy reflux condensate to said recycling cracking zone, combining aforesaid light gas oil condensates and directing the combined constituents to a second recycling cracking zone wherein they are subjected to cracking conditions of temperature and pressure to effect conversion into lower boiling hydrocarbons, passing resultant cracked products from the second recycling cracking zone to a third separating zone wherein vapors separate from residue, passing resultant separated vapors to a third fractionating zone wherein the vapors are fractionated to form a heavy reflux condensate, an intermediate condensate and a light distillate, cycling the heavy reflux condensate from the third iractionating zone to the second recycling cracking zone, introducing said lighter reflux condensate from the second fractionating zone to the third fractionating zone wherein it is subjected to vaporization and resultant vapors are subjected to fractional condensation to thereby combine constituents of said lighter reflux condensate with the intermediate condensate in the third fractionating zone and withdrawing said intermediate condensate as a product of the process.

CHARLES W. NOFSINGER. 

